1. Field of the Invention
The invention relates to a joining method, more particularly, a joining method for joining together fiber-reinforced resin members in which reinforcing fiber material is mixed into a matrix resin, for example.
2. Description of Related Art
Methods that use vibration, ultrasonic waves, friction between resin members, and heat plates, for example, are known as methods for joining fiber-reinforced resin members in which reinforcing fiber material such as glass fiber or carbon fiber is included in resin (matrix resin) or a resin member made of thermoplastic resin.
However, with all of these methods, the joining surfaces are pressed together with a predetermined pressure while the area near the joining surfaces is melted, so burr is generated at the joint portion, which is problematic. Also, the fiber-reinforced resin material is strong against stress in a direction parallel to the direction of orientation of the fibers, and weak against stress in a direction orthogonal to the direction of orientation of the fibers. Therefore, although it is desirable to orient the fibers in the direction orthogonal to the joining surface when joining these kinds of fiber-reinforced resin members together, if the members are pressed on in the direction orthogonal to the joining surface when they are joined together as described above, the fibers near the joining surface will be oriented so that they become parallel to the joining surface, which is problematic.
To counter this kind of problem, Japanese Patent Application Publication No. 2003-145625 (JP 2003-145625 A) describes a joining method for fiber-reinforced resin members that enables high joint strength to be obtained while suppressing the generation of burr.
The joining method for fiber-reinforced thermal flexible resin members described in JP 2003-145625 A is a method in which at least one of a first thermoplastic resin member and a second thermoplastic resin member is made of fiber-reinforced resin, and which involves first abutting the first thermoplastic resin member and the second thermoplastic resin member together, and then pressing a rotating probe against a surface portion of the first thermoplastic resin member and the second thermoplastic resin member that includes a predetermined portion of a surface boundary line between the first thermoplastic resin member and the second thermoplastic resin member, and moving the probe along the surface boundary line.
According to the joining method for fiber-reinforced thermal flexible resin members described in JP 2003-145625 A, the fibers in the thermoplastic resin members that have melted at a front portion of the probe are caught by the rotation of the probe, such that their orientation changes. The fibers then harden while oriented in a direction substantially orthogonal to the abutting surface of the abutting portion at a rear portion of the probe, thereby enabling the join strength of the members to be increased.
However, in the joining method of fiber-reinforced thermal flexible resin members described in JP 2003-145625 A, the rotating probe is pressed against the surface portion of the first thermoplastic resin member and the second thermoplastic resin member, and moved along the surface boundary line thereof. Therefore, the direction of orientation of the fibers inside the first thermoplastic resin member and the second thermoplastic resin member is unable to be changed, so the problem in which the joint strength of the members is unable to be sufficiently increased may remain.